Herd milk production performance is generally evaluated using the herd's average 305-day milk production (HM305). Economic comparisons between herds are also often made using HM305. Comparing herds is thus based on summarized milk production, and not on the form of the lactation curves of the cows within the herd. Cow lactation curve characteristics can be aggregated on a calendar year basis to herd lactation curve characteristics (HLCC) (herd magnitude, herd time to peak yield and herd persistency). Thus far, no literature has evaluated whether the shape of the lactation curve (described by HLCC) is better able to explain the economic variation of herds than summarized milk production such as HM305 does. This study aims to determine whether HM305 or HLCC is better able to explain the variation in economic performance between herds. To do so, we evaluated 8 years of Dutch longitudinal data on milk production and the financial accounts of 1,664 herds. Cow lactation curve characteristics were calculated through lactation curve modeling and aggregated to HLCC on a calendar year basis for two parity groups (primiparous cows and multiparous cows). Using income over feed cost per cow (IOFC-cow) or per 100 kg milk (IOFC-milk) as the dependent variable separately, we developed four linear mixed models. Two models were used to analyse the association between herd economic performance and HLCC; the other two models were used to analyse the association between herd economic performance and HM305. A Cox test and J test were used to compare two non-nested models to investigate whether HM305 or HLCC better explain IOFC. The average IOFC-cow was €2,305 (SD = 408) per year, while the average IOFC-milk was €32.1 (SD = 4.6). Results showed that HLCC and HM305 explain the same amount of variance of IOFC-cow or IOFC-milk. IOFC-cow was associated with HM305 and HLCC (except herd time to peak yield for primiparous cows). Herd magnitude was most strongly associated with IOFC-cow, followed by herd persistency and herd time to peak yield of multiparous cows. IOFC-milk was not associated with HM305 or HLCC (except for a weak negative association with herd persistency for primiparous cows). IOFC-cow and IOFC-milk were driven most by time effects. In conclusion, HLCC and HM305 explain the same amount of variance in IOFC-cow or IOFC-milk. HLCC is more computationally expensive, while HM305 is more readily available.

AbstractThe aim of this study was to identify genomic regions associated with 305‐day milk yield and lactation curve parameters on primiparous (n = 9,910) and multiparous (n = 11,158) Holstein cows. The SNP solutions were estimated using a weighted single‐step genomic BLUP approach and imputed high‐density panel (777k) genotypes. The proportion of genetic variance explained by windows of 50 consecutive SNP (with an average of 165 Kb) was calculated, and regions that accounted for more than 0.50% of the variance were used to search for candidate genes. Estimated heritabilities were 0.37, 0.34, 0.17, 0.12, 0.30 and 0.19, respectively, for 305‐day milk yield, peak yield, peak time, ramp, scale and decay for primiparous cows. Genetic correlations of 305‐day milk yield with peak yield, peak time, ramp, scale and decay in primiparous cows were 0.99, 0.63, 0.20, 0.97 and −0.52, respectively. The results identified three windows on BTA14 associated with 305‐day milk yield and the parameters of lactation curve in primi‐ and multiparous cows. Previously proposed candidate genes for milk yield supported by this work include GRINA, CYHR1, FOXH1, TONSL, PPP1R16A, ARHGAP39, MAF1, OPLAH and MROH1, whereas newly identified candidate genes are MIR2308, ZNF7, ZNF34, SLURP1, MAFA and KIFC2 (BTA14). The protein lipidation biological process term, which plays a key role in controlling protein localization and function, was identified as the most important term enriched by the identified genes.

37 cases of right- and left-sided abomasal displacement were operated and the abomasum was fixed ventrally. The surgical cases were matched with controls in the same herd and the milk yield was compared over a 12-month period before and after surgery. From the 6th to the 12th month after surgery, the surgical cases produced 5-10 lb more milk than the controls. It was suggested that subclinical abomasal displacement is a common cause of low performance in high-yielding dairy cows. This paper should be viewed as a case study, not a full analysis of a complex disease. The results suggest strongly that there may be positive effects of abomasopexy beyond simply cutting the losses associated with this production disease.

Optimal growth rate for dairy heifers has been defined as the rate that will allow heifers to develop to their lactation potential at the desired age and with minimum expense. Animals that follow a normal growth curve are likely to be more healthy, and grown at lower cost, than animals whose growth deviated from the normal curve. This paper describes a computer program, (readily available to veterinarians as “shareware”) that can be used to compare animals in a herd to growth standards. The program plots the deviation of each animal’s measured height and weight from standards for an animal of the same bred and age. A representative sample (25% or more) of heifers from a farm should be measured and charted. The chart produced is an efficient screen for problems in youngstock management. Frequently problems in youngstock management. Frequently particular husbandry problems will be suggested by characteristic patterns of abnormal growth. Heifer growth charts have been used in various ways for many years. Computerization saves a great deal of time and effort in plotting points on paper as well as greatly decreasing the chances for errors in plotting points. The deviation chart format emphasizes problems while minimizing clutter. The program will run on IBM-compatible microcomputers running MS-DOS or PC-DOS without additional software and is configurable to use either Metric English units.